Braking System for Gyroscopic Boat Roll Stabilizer

ABSTRACT

A gyroscopic boat roll stabilizer for a boat comprises a gimbal, having a gimbal axis, an enclosure mounted to the gimbal and configured to precess about a gimbal axis, a flywheel assembly rotatably mounted inside the enclosure for generating a torque that is applied to counter a rolling motion of the boat, and a braking system for controlling precession of the enclosure. The braking system is configured to enable precession in the first and second directions of up to at least 45 degrees.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/828,845 filed 3 Apr. 2019, the entire disclosure of which is beinghereby incorporated by reference herein.

TECHNICAL FIELD

The present disclosure relates generally to boat roll stabilizers forreducing the sideways rolling motion of a boat and, more particularly,to an improved braking system for controlled moment gyroscopes.

BACKGROUND

The sideways rolling motion of a boat can create safety problems forpassengers and crew on boats, as well as cause discomfort to passengersnot accustomed to the rolling motion of the boat. A number oftechnologies currently exist to reduce the sideways rolling motion of aship. One technology currently in use is active fin stabilization.Stabilizer fins are attached to the hull of the ship beneath thewaterline and generate lift to reduce the roll of the ship due to windor waves. In the case of active fin stabilization, the motion of theship is sensed and the angle of the fin is controlled based on themotion of the ship to generate a force to counteract the roll. Finstabilization is most commonly used on large ships and are effectivewhen the ship is underway. Fin stabilization technology is not usedfrequently in smaller boats and is generally not effective when the boatis at rest. Stabilizer fins also add to the drag of the hull and aresusceptible to damage.

Gyroscopic boat stabilization is another technology for roll suppressionthat is based on the gyroscopic effect. A control moment gyroscope (CMG)is mounted in the boat and generates a torque that can be used tocounteract the rolling motion of the boat. The CMG includes a flywheelthat spins at a high speed. A controller senses the attitude of the boatand uses the energy stored in the flywheel to “correct” the attitude ofthe boat by applying a torque to the hull counteracting the rollingmotion of the boat. CMGs work not only when a boat is underway, but alsowhen the boat is at rest. CMGs are also less expensive than stabilizerfins, do not add to the drag of the hull, and are not exposed to risk ofdamage.

Although, CMGs are gaining in popularity, particularly for smallerfishing boats and yachts, this technology has some limitations. CMGsrely on a braking system to control the precession of the flywheel. Inprior art CMGs, the design of the braking system constrains theprecession of the flywheel to about +/−22 degrees, which may not besufficient to effectively counter the rolling motion of the boat.Further, the resistance of the braking systems imposes limitations onthe rate of precession, which affects the responsive of the CMG to thewave motion.

SUMMARY

The present disclosure relates to a gyroscopic boat roll stabilizerconfigured to be installed in a boat. The boat roll stabilizer comprisesa gimbal, having a gimbal axis, an enclosure mounted to the gimbal andconfigured to precess about a gimbal axis, a flywheel assembly rotatablymounted inside the enclosure for generating a torque that is applied tocounter a rolling motion of the boat, and a braking system forcontrolling precession of the enclosure. The braking system isconfigured to enable precession in the first and second directions of upto at least 45 degrees.

According to another aspect of the disclosure, the braking systemcomprises a first actuator connected between the support frame and theenclosure to resist precession in a first direction about the gimbalaxis, and a second actuator connected between the support frame and theenclosure to resist precession in a second direction about the gimbalaxis. The first actuator and the second actuator both connect to theenclosure on the same side of a transverse plane including the gimbalaxis, and on different sides of a frontal plane including the gimbalaxis.

According to another aspect of the disclosure, each actuator comprises afluid cylinder and a lockout valve mounted to the fluid cylinder of theactuator. The lockout valve is movable between a locked positionpreventing precession of the enclosure and an unlocked position. Thelockout valves are in fluid communication with the piston side of thefluid cylinders. In one embodiment, a manifold is disposed in a fluidflow path between the first and second actuators. A first port on eachlockout valve is in fluid communication with the manifold, while asecond port on each lockout valve is in fluid communication with the rodside of the fluid cylinder. A fluid line connects the first port of thelockout valve on the actuator to the manifold.

According to another aspect of the disclosure, each of the actuatorsfurther comprises a bypass line connecting the second port of thelockout valve and configured to communicate fluid directly between thecylinder side and rod side of the fluid cylinder of the actuatorwithout.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate a boat equipped with a boat roll stabilizer.

FIG. 2 is a perspective view of the boat roll stabilizer showing thegimbal and enclosure.

FIG. 3 is a cross section of the enclosure for the boat roll stabilizer,showing the flywheel assembly.

FIG. 4 is an elevation view of a boat roll stabilizer with the enclosurein a neutral or vertical position.

FIG. 5 is an elevation view of a boat roll stabilizer with the enclosurerotated at a 45° angle.

FIG. 6 is a schematic block diagram of a torque control system for theboat roll stabilizer.

FIG. 7 is a perspective view of a braking system for a boat rollstabilizer.

FIG. 8 a schematic diagram of a braking system for a boat rollstabilizer.

FIG. 9 is a perspective view of the manifold for the braking system.

FIG. 10 is a section view of the manifold for the braking system.

FIG. 11 is a graph of the roll resistance to a large rolling wave of aboat roll stabilizer.as herein described compared to the roll resistanceof a conventional boat roll stabilizer.

FIG. 12 is a graph of the roll resistance to a large short wave of aboat roll stabilizer.as herein described compared to the roll resistanceof a conventional boat roll stabilizer.

DETAILED DESCRIPTION

Referring now to the drawings, FIGS. 1A and 1B illustrate a CMG 10mounted in a boat 5 for roll stabilization. Multiple embodiments of theCMG 10 are described. For convenience, similar reference numbers areused in the following description of the embodiments to indicate similarelements in each of the embodiments.

The main functional elements of the CMG 10 comprise a single-axis gimbal20, an enclosure 30 mounted to the gimbal 20 for rotation about a gimbalaxis, a flywheel assembly 40 mounted by bearings 50 inside the enclosure30, a motor 60 to rotate the flywheel assembly 40, and a torque controlsystem 100 (FIG. 6) to control precession of the flywheel 42 so that theenergy of the flywheel assembly 40 is transferred to the hull of theboat 5 to counteract rolling motions.

The gimbal 20 comprises a support frame 22 that configured to besecurely mounted in the boat 5. Preferably, the gimbal 20 is mountedalong a longitudinal axis (LA) of the boat 5 with the gimbal axis Gextending transverse to the longitudinal axis of the boat 5.Conventionally, the gimbal 20 is mounted in the hull of the boat 5, butcould be mounted at any location. The enclosure 30 is rotatably mountedto the support frame 22 by spherical roller bearings 28 housed in pillowblocks so as to rotate about the gimbal axis G extending transverselyacross the boat 5. For this purpose, the enclosure 30 includes twogimbal shafts 32 projecting from diametrically opposed sides of theenclosure 30. The gimbal shafts 32 are received in the sphericalbearings 28 to allow the enclosure 30 and flywheel assembly 40 to rotateor precess about the gimbal axis G in the fore and aft directions.

The enclosure 30 is generally spherical in form and comprises two mainhousing sections 34 and two cover plates 36. The two main housingsection 34 join along a plane that bisects the spherical enclosure 30.The cover plates 36 join the main housing sections along respectiveplanes closer to the “poles” of the spherical enclosure 30. All jointsin the enclosure 30 are sealed to maintain a below-ambient pressurewithin the enclosure 30 to reduce aerodynamic drag on the flywheelassembly 40.

The flywheel assembly 40 comprises a flywheel 42 and shaft 44 that ismounted for rotation inside the enclosure 30 so that the rotational axisF of the flywheel 42 is perpendicular to the gimbal axis G. Thus, whenthe boat 5 is level, the rotational axis F of the flywheel shaft 44 willbe in the vertical direction, i.e., perpendicular to the deck of theboat. The flywheel 42 and shaft 44 may be formed as a unitary piece, ormay comprise two separate components. In one exemplary embodiment, thediameter of the flywheel 42 is approximately 20.5 inches and theflywheel assembly 40 has a total weight of about 614 lbs. The flywheelassembly 40 has a moment of inertia of about 32,273 lb in². When rotatedat a rate of 9000 rpm, the angular momentum of the flywheel assembly 40is about 211,225 lbm ft²/s.

The flywheel assembly 40 is supported by upper and lower bearingassemblies inside the enclosure 30. Each bearing assembly comprises abearing 50 mounted within a bearing block 58. Each bearing 50 comprisesan inner race 52 that contacts and rotates with the flywheel shaft 44,an outer race 54 that is fixed inside the bearing block 58, and a ball56 disposed between the inner and outer races 52, 54. The bearing blocks58 are secured to the interior of the enclosure. Seals (not shown) aredisposed on the top and bottom of the bearings 50 to contain lubricantin the bearings 50. Each end of the flywheel shaft 44 includes a cavitywith a heat sink inserted therein to dissipate heat as described in U.S.Provisional Application No. 62/768,356 filed Nov. 18, 2018, which isincorporated herein in its entirety by reference.

The motor 60 rotates the flywheel assembly 40 at a high rate of speed(e.g., 9000 rpm). Although the motor 60 is shown mounted inside theenclosure 30, it is also possible to mount the motor 60 on the exteriorof the enclosure 30. In one embodiment, the motor 60 comprises operateson 230 volt single phase AC power and is able to accelerate a flywheelassembly with a moment of inertia of about 32,273 lb in² flywheel fromrest to a rotational speed of 9000 rpm preferably in about 30 minutes orless for an average acceleration of about 5 rpm/s, and more preferablyin about 20 minutes or less for an average acceleration of about 7.75rpm/s, and even more preferably in about 10 minutes or less for anaverage acceleration of about 15 rpm/s (or 1.57 radians/s²).

The torque control system 100, shown in FIG. 6, controls the precessionof the flywheel 42 about the gimbal access. The rolling motion of a boat5 caused by wave action can be characterized by a roll angle and rollrate. The rolling motion causes the flywheel 42 to precess about thegimbal axis. Sensors 104, 106 measure the roll angle and roll raterespectively, which are fed to a controller 102. The controller 102generates control signals to control an active braking system 110 orother torque applying device that controls the precession of theflywheel 42. By controlling the precession, the flywheel assembly 40generates a torque to counteract the rolling motion. This torque istransferred through the gimbal 20 to the boat 5 to dampen the roll ofthe boat 5.

In conventional braking systems 110 for CMGs 10, the design of thebraking system constrains the precession of the flywheel to about +/−22degrees, which may not be sufficient to effectively counter the rollingmotion of the boat. Further, the resistance of the braking systems 110imposes limitations on the rate of precession, which affects theresponsive of the CMG 10 to wave motion.

According to one aspect of the disclosure, the braking system 110 isdesigned to enable the flywheel 42 to precess up to about +/−45 degrees.An exemplary embodiment of the braking system 110 is shown in FIGS. 7and 8. FIG. 7 is a reverse perspective view of the braking system 110.As seen in FIG. 7, the braking system 110 comprises a pair of actuatorassemblies 120 that control the precession of the flywheel 42 about thegimbal axis, and a manifold assembly 150 for transferring fluid betweenthe opposing cylinders 120 when the flywheel. Hydraulic lines connectthe fluid cylinders 120 with the manifold assembly 150 to form a closedfluid flow path between the cylinders 120.

FIG. 8 is a schematic diagram of the braking system 110. As seen in FIG.8, the actuator assemblies 120 each comprise a fluid cylinder 122 havinga housing 124, piston 126, and piston rod 128. The fluid cylinders 122each include a piston side port and a rod side port. A lockout valve 130is mounted on the housing 124 of the fluid cylinder 122 and is in fluidcommunication with the piston side port of each fluid cylinder 122. Thelockout valve 130 is normally open and is closed by actuation of asolenoid 132. In one embodiment, the housing of the lockout valve 130 issecured to or integrally formed with the housing 124 of the fluidcylinder 122 to form a unitary assembly. Each fluid cylinder 122 ispivotally connected at one end to the support frame 22 and at the otherend to the enclosure 30. The housing 124 of the fluid cylinder 122pivotally connects to the support frame 22 and the piston rod 128pivotally connects to the enclosure 30 via a connecting plate 140 (FIG.7), although this arrangement could be revised.

The connecting plate 140, shown best in FIG. 7, bolts to the exterior ofthe enclosure 30 and includes two pivot pins 142 that are rotatablyjournaled in bushings or bearings (not shown) disposed at the end ofrespective piston rods 128. The connecting plate 140 is symmetricalabout a frontal plane and the pivot pins 142 are offset from the frontalplane by a distance D. As used herein, the term “frontal plane” refersto a vertical plane (when the enclosure 30 is in a neutral position)that includes the gimbal axis and divides the enclosure 30 into frontand back sections. The axes of the pivot pins 142 are parallel to thefrontal plane. Three bolts 144 pass through corresponding openings inthe connecting plate 140 and thread into threaded holes (not shown) inthe enclosure 30 to secure the connecting pale 140 to the enclosure.

Due to the mechanical arrangement of the braking system 110, theenclosure 30 is able to precess up to about +/−45 degrees without anymechanical interference compared to about +/−22.5 degrees for prior artdesigns. The greater degree of precession enables a greater peak rolltorque to be achieved.

Referring back to FIG. 8, the manifold assembly 150 comprises a mainvalve 152, two check valves 154, two pressure relief valves 156, and twoaccumulators 158. The main valve 152 is mounted to the manifold block151 as shown in FIG. 9 and has four ports labeled A, B, P and Trespectively and is controlled by a solenoid 134. Ports P and B connectvia fluid lines 160A and 160B to the normally closed lockout valves 130in actuator assemblies 120A and 120B respectively. Ports A and T connectthe main valve 152 to respective accumulators 158. Fluid flowing intothe main valve via port P exits via port A. Fluid flowing into the mainvalve 152 via port B exits via port T. The check valves 154 control thedirection of the fluid flow through the main valve 152 and prevent backflow into ports A and T of the main valve 152. The pressure reliefvalves 156 prevent over-pressurization of the fluid in the fluidcomponents of the braking assembly 10 due to thermal expansion of fluidwhen the enclosure 30 is locked. The main valve 152 and lockout valves130 are controlled by solenoids 132 and 134 respectively, which areactuated by the controller 102.

When the enclosure 30 precesses such that the piston 126 of fluidcylinder 122A retracts, fluid flows from the piston side of the fluidcylinder 122A through the lockout valve 130. A portion of the fluidexiting the fluid cylinder 122 flows through a bypass line 162A to therod side of the fluid cylinder 122A. The rod side of the cylinder isunable to accommodate all of the fluid exiting the piston side of thecylinder due to the volume of the rod 128. Therefore, a portion of thefluid flows into port P of the main valve 152. From the main valve 152,the fluid exits port A, flows through the check valve 154, whichprevents backflow into the manifold 150 and through line 160B to thelockout valve 130B on the piston side of the fluid cylinder 122B. Whenthe enclosure 30 precesses in the opposite direction, the fluid flowreverses.

The accumulators 158 provide additional capacity in case the fluidexpands due to heat, or due to imbalance of the fluid flow. The heatingor imbalance of the fluid flow will create a higher pressure in the mainvalve 152, which in turn will cause any excess fluid to flow via ports Aand T into the accumulators 158. Because ports A and T are on the lowpressure side of the main valve, the cycling of fluid into and out ofthe accumulators is minimized.

In some embodiments, a cooling circuit 170 can be provided to dissipateheat generated by the movement of fluid through the manifold 150. Acoolant source 172 connects to two coolant ports 174 on the manifold150. The coolant ports 174, in turn connect to coolant passages 176inside the manifold block 151 as shown in FIG. 10. The coolant passages176 closely surround the fluid passages 178 connecting to ports A, B, Pand T of the main valve 152 to dissipate the heat generated by the fluidflow through the main valve 152.

The design of the fluid flow path minimizes the amount of fluid thatneeds to flow through the main valve 152, which reduces the overallresistance due to fluid flow. The bypass lines 162A and 162B provide avery short fluid flow path between the piston side and rod side of thefluid cylinders 122A and 12B for a majority of the fluid flow withouthaving the pass through the manifold assembly 150. Thus, only a smallfluid flow needs to pass through the longer lines 160A and 160B. As aresult, the frictional losses due to the fluid flow are greatly reduced,which in turn allows greater acceleration in the rate of precession sothat the CMG 10 responds more quickly to the roll motion caused by awave.

The solenoids 132 on the lockout valve 130 and the solenoid 134 on themain valve 152 provide a mechanism to lock the enclosure 30 to preventprecession of the enclosure 30. The lockout valves 130 and main valve152 are biased to a locked position and the solenoid valves 132 and 134are actuated to unlock the valves 130, 152. In the locked position,fluid flow through the lockout valve 130 and main valve 152 isprevented, which prevents precession of the enclosure 130. Normally, theenclosure 30 is locked when the flywheel 142 is spinning up to minimizebearing friction. When the flywheel 142 reaches a predetermined speed,the lockout valves 130 and main valve 152 are unlocked. The time ittakes to reach the predetermined speed is referred to as the time toengage and is an important consideration for consumer enjoyment.Preferably, a low time to engage is desired so that the benefits of rollreduction are realized sooner.

The combination of the increased precession of the enclosure 30 and thefaster rate of precession allows more counter torque to be generatedmore quickly by the CMG 10 as compared to prior art designs. It has beenestimated that the peak roll torque can be increased by 5-10% due to theimprovements of the braking system 110.

FIGS. 11 and 12 illustrates how the improvements of the braking systemtranslate to roll reduction. FIGS. 11 and 12 graphically illustrate theestimated roll resistance for the CMG 10 as herein described with theroll resistance of a similar prior art design for a large rolling wave(FIG. 9) and a large short wave (FIG. 10).

What is claimed is:
 1. A gyroscopic boat roll stabilizer configured tobe installed in a boat, comprising: a gimbal including a support frameand enclosure configured to precess about a gimbal axis; a flywheelassembly rotatably mounted inside the enclosure for generating a torquethat is applied to counter a rolling motion of the boat; a brakingsystem for controlling precession of the enclosure, the braking systemcomprising: a first actuator connected between the support frame and theenclosure to resist precession in a first direction about the gimbalaxis; a second actuator connected between the support frame and theenclosure to resist precession in a second direction about the gimbalaxis; wherein the first actuator and the second actuator are configuredto enable precession in the first and second directions of up to atleast 45 degrees.
 2. The gyroscopic boat roll stabilizer of claim 1wherein the first actuator and the second actuator both connect to theenclosure on the same side of a transverse plane including the gimbalaxis, and on different sides of a frontal plane including the gimbalaxis.
 3. The gyroscopic boat roll stabilizer of claim 2 furthercomprising a connecting plate having two pivot pins for pivotallyconnecting the actuators to the enclosure.
 4. The gyroscopic boat rollstabilizer of claim 3 wherein the pivot pins are offset from the frontalplane.
 5. The gyroscopic boat roll stabilizer of claim 1 wherein thefirst and second actuators each comprise a fluid cylinder and a lockoutvalve mounted to the fluid cylinder of the actuator, wherein the lockoutvalve is movable between a locked position preventing precession of theenclosure and an unlocked position.
 6. The gyroscopic boat rollstabilizer of claim 5 wherein the lockout valves are in fluidcommunication with the first end of the fluid cylinders.
 7. Thegyroscopic boat roll stabilizer of claim 5 wherein each of the lockoutvalves further comprises: a first port in fluid communication with themanifold; and a second port in fluid communication with the second endof the fluid cylinder.
 8. The gyroscopic boat roll stabilizer of claim 7further comprising: a manifold disposed in a fluid flow path between thefirst and second actuators; a fluid line for each actuator connectingthe first port of the lockout valve on the actuator to the manifold. 9.The gyroscopic boat roll stabilizer of claim 8 wherein each of theactuators further comprises a bypass line connecting the second port ofthe lockout valve and configured to communicate fluid directly betweenthe cylinder side and second end of the fluid cylinder of the actuatorwithout.
 10. The gyroscopic boat roll stabilizer of claim 5 wherein thelockout valve for each actuator is integrally with a housing of thefluid cylinder.
 11. A gyroscopic boat roll stabilizer configured to beinstalled in a boat, comprising: a gimbal including a support frame andenclosure configured to precess about a gimbal axis; a flywheel assemblyrotatably mounted inside the enclosure for generating a torque that isapplied to counter a rolling motion of the boat; a braking system forcontrolling precession of the enclosure, the braking system comprising:a first actuator including a first fluid cylinder and a first lockoutvalve, the first fluid cylinder being connected between the supportframe and the enclosure to resist precession in a first direction aboutthe gimbal axis, a second actuator including a second fluid cylinder anda second lockout valve, the second fluid cylinder being connectedbetween the support frame and the enclosure to resist precession in asecond direction about the gimbal axis; wherein each of the first andsecond lockout valves is movable between a locked position preventingprecession of the enclosure and an unlocked position.
 12. The gyroscopicboat roll stabilizer of claim 11 wherein the lockout valves are in fluidcommunication with the first end of the fluid cylinders.
 13. Thegyroscopic boat roll stabilizer of claim 11 wherein each of the lockoutvalves further comprises: a first port in fluid communication with themanifold; and a second port in fluid communication with the second endof the fluid cylinder.
 14. The gyroscopic boat roll stabilizer of claim13 further comprising: a manifold disposed in a fluid flow path betweenthe first and second actuators; a fluid line for each actuatorconnecting the first port of the lockout valve on the actuator to themanifold.
 15. The gyroscopic boat roll stabilizer of claim 14 whereineach of the actuators further comprises a bypass line connecting thesecond port of the lockout valve and configured to communicate fluiddirectly between the cylinder side and second end of the fluid cylinderof the actuator without.
 16. The gyroscopic boat roll stabilizer ofclaim 11 wherein the lockout valve for each actuator is integrally witha housing of the fluid cylinder.
 17. A gyroscopic boat roll stabilizerconfigured to be installed in a boat, comprising: a gimbal including asupport frame and enclosure configured to precess about a gimbal axis; aflywheel assembly rotatably mounted inside the enclosure for generatinga torque that is applied to counter a rolling motion of the boat; abraking system for controlling precession of the enclosure, the brakingsystem comprising: a first actuator including a first fluid cylinderconnected between the support frame and the enclosure to resistprecession in a first direction about the gimbal axis, a second actuatorincluding a second fluid cylinder connected between the support frameand the enclosure to resist precession in a second direction about thegimbal axis; a manifold connected in a fluid flow path between the firstand second fluid cylinders; a first bypass line establishing a fluid lowpath between first and second ends of the first cylinder that bypassesthe manifold; and a second bypass line establishing a fluid low pathbetween first and second ends of the first cylinder that bypasses themanifold.
 18. The gyroscopic boat roll stabilizer of claim 1 wherein thefirst and second actuators each further comprise a lockout valve movablebetween a locked position preventing precession of the enclosure and anunlocked position.
 19. The gyroscopic boat roll stabilizer of claim 18wherein the lockout valves are in fluid communication with a first endof the fluid cylinders.
 20. The gyroscopic boat roll stabilizer of claim19 wherein each of the lockout valves further comprises: a first port influid communication with the manifold; and a second port in fluidcommunication with the second end of the fluid cylinder.
 21. Thegyroscopic boat roll stabilizer of claim 20 further comprising a fluidline for each actuator connecting the first port of the lockout valve onthe actuator to the manifold.
 22. The gyroscopic boat roll stabilizer ofclaim 18 wherein the lockout valve for each actuator is integrally witha housing of the fluid cylinder.